Display devices equipped with touch panel devices, e.g. liquid crystal displays equipped with touch panel devices, are used for mobile phones and other mobile electronic devices, consumer electronics, and unmanned reception devices and other stationary-type customer assistance terminals.
As touch panel devices, contact film types, electrostatic capacity types, photosensor types, etc. are known. Among these, electrostatic capacitance-type touch panel devices are excellent in transmission rate of light from the display devices, durability, etc. Further, electrostatic capacitance-type touch panel devices are excellent in the point that they enable multipoint detection (multi-touch) by arranging, as a vertical and horizontal two-dimensional matrix, two types of position-detecting electrodes consisting of vertical position-detecting electrodes and horizontal position-detecting electrodes (Patent Document 1).
Incidentally, in a display device equipped with a touch panel device, the touch panel device is not entirely bonded to the display surface of the display device. Rather, in the general practice, an air layer of about 0.5 to 1.0 mm is provided between the touch panel device and display device (Patent Documents 2 and 3).
The reasons of providing an air layer of about 0.5 to 1.0 mm between the touch panel device and the display device are, e.g., the following (1) and (2):
(1) Since a touch panel device and a display device differ in production conditions, it is difficult or impossible to integrally produce the touch panel device and the display device so as to completely eliminate any clearance. Further, when the touch panel device and the display device are not integrally produced, if it is found, at the final stage of production, that the touch panel device does not suitably work, it is possible to detach the touch panel device, which does not suitably work, from the display surface of the display device, and exchange it with a new touch panel device. Therefore, the touch panel device and the display device are preferably not integrally produced.
(2) If the thickness of the air layer between the touch panel device and the display device is too small, the light reflected at the interface between the touch panel device and the air layer (i.e., the top side interface of the air layer), and the light reflected at the interface between the display device and the air layer (i.e., the bottom side interface of the air layer) interfere with each other, and thereby Newton rings (moire) are formed. Incidentally, when the thickness of the air layer between the touch panel device and the display device is sufficiently large, e.g. when the thickness of the air layer is about 1.0 mm, the difference in paths of the reflected lights, which are respectively reflected at the top and bottom side interfaces of the air layer, is large, and therefore no interference substantially occurs.
Regarding the Newton ring-formation problem in item (2) above, Patent Documents 2 and 3 propose to fill the air layer between the touch panel device and the display device with a resin material to form a resin layer, and thereby eliminate reflection at the top and bottom side interfaces of the air layer.
However, when filling with a resin material, even if finding, at the final stage of production, that the touch panel device does not suitably work, it is sometimes difficult to detach the touch panel device, which does not suitably word, from the display surface of the display device, and exchange it with a new touch panel device. Further, when filling with a resin material, it is sometimes difficult to fill it with preventing air bubbles from entering into the resin material. Still further, when filling with a resin material, naturally the weight increases.
Further, regarding the Newton ring-formation problem in item (2) above, Patent Document 3 proposes to provide unevenness to the surface of the touch panel device and the air layer-side surface of the display device, and thereby prevent reflection at the top and bottom side interfaces of the air layer.
However, when providing unevenness to the air-layer-side surfaces with unevenness, there is a problem of increasing in the haze due to the unevenness.